Modulating system



ept. 2., 1924. r 1,506,742

C. LE G. FORTESCUE MODULAT ING SYSTEM Filed June 25. 1921 INVENTOR J C Jfiarks Zedfa'r/eswa ATTORNEY latented Sept. 2, 1924.

UNIT

CHARLES LE FGRTESCUE, 0F PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WEST- INGHOUSE ELECTRIC AN}? MANUFACTURZNG GOMEANY, A. CORPORATION OF PENNSYLVANIA.

Application filed June 25,

To all whom it may concern:

3e it known that I, GHAnLns LE G. Fon- TESOUE, a subject of the King of England, and a resident of Pittsburgl in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Modulating Systems, of wh ch the following is a specification.

My invention relates to means for controlling current of radio frequency and more particularly it relates to means for controlling the input to an antenna system in radio telegraphy.

()ne object of my invention is to devise a system for the control of radio-frequency input to an antenna in which there will be no arcing between the contacts.

Another object of my invention is to provide a radio modulation system in which the period of oscillation of the antenna is reduced below radio frequency when a message is not being sent.

A still further ob ect of my invention is to devise a system for controlling the input to an antenna in radio telegraphy in which the load on the generator is substantially constant in either the up position or the down position of the telegraph key.

The problem of control of the high-frequency radio input to an antenna in radio telegraphy has always been a dil' ficult one. In my system, I employ a tuned antenna circuit having an inductance coil therein, and located in inductive relation to the in ductance coil is a controller primary inductance coil. A balancing inductance coil is connected in parallel with the controller primary inductance coil through contacts controlled by a telegraph key. A source of high-frequency current is connected to the middle points of the controller primary and balancing inductance coils, and the key controls the flow of current through said coils. Means may also be provided for maintaining the load on the high-frequency source substantially constant.

By reason of the coupling of the antenna inductance coil to the controller primary in- 1921. $eria1 No. 480,372.

ductance coil, when the key is in the up position, no effective power is delivered through the transformer coupling, and the frequency of oscillation of the antenna circuit is greatly reduced, as compared with the operating frequency. This takes place by reason of the fact that, in the down position of the key, when the transformer is de livering power to the antenna, the primary coil of the transformer coupling is, in effect, short-circuited by the high-frequency source.

In the drawing, the single figure is a diagrammatic View illustrating my system for controlling the delivery of power to the antenna.

Referring to the drawing, I have shown an antenna 1, having a variable tuning inductance coil 2 and a coupling inductance coil 3, whence the system is connected to ground. In the arrangement, I have shown no tuning condenser, assuming that, in the particular instance, the effective capacity of the circuit will be sullicient to provide the necessary ratio of the capacity to inductance for the tuning of the circuit to the desired frequency. By the adjustment of the tuning inductance coil 2, the circuit may be tuned to any desired frequency.

The coupling inductance coil 3 is the secondary member of a transformer 4, the primary winding of which is provided with a mid-tap 5, separating the same into two equal coils 6 and 7. A source of high-frequency alternating current, diagrammatically illustrated as a hi 'h-frequency alternator 8, is connected between the mid-tap 5 and a midtap 9 of a two-part balancing inductance device 10, 11 of relatively high inductance. The outer end of the controller primary inductance coil 7 is connected to the outer end of the balancing inductance coil 11, and the outer end of the controller primary coil 6 is connected to a contact member 12, which is adapted to be engaged by a contact member 13 on a telegraph key 14 in the up position thereof. The telegraph key 14: is connected to the outer end of the balancing inductance coil 10. Connected to I through 13 and the upper the balancing inductance coil 11 is a con tact member 15, adapted to be engaged by the contact member 13 in the down position of the key.

In operation, the alternating-current enerator 8 generates radio-frequency osc1llations of the desired frequency and the antenna circuit is normally tuned to said frequency. In the down position of the key, the contact member 13 and the contact member 15 are in engagement, and a circuit is closed from one side of the alternator '8, through the lower primary inductance coil 7 and through the lower balancing inductance coil 11, back to the radio-frequency generator 8. At thesame time, a circuit is closed through the shunt circuit comprising the contact member 15, the contact member balancing inductance coil current flows non-inductively the balancing inductance coils 10 and 11 in the down position of the key.

By reason of the inductive action between the antenna coupling coil 3 and the controller primary coil 7 oscillations are set up within the antenna system.

' When the key 14- is moved to its up position, current flows from one side of the radio-frequency generator 8 to the mid-tap of the primary Winding and, in the upward direction, through the upper half 6, through the contact member 12, the contact member 13 on the key 14 and the upper balancing coil 10, and back to the other side of the generator 8. Simultaneously, current flows from the first-mentioned side of the generator 8 through the lower con troller primary coil 7, upward through the lower balancing coil 11 and to the other side of the generator 8. By reason of the directions from the 10. Thus,

flowof current in both middle towards the ends of the controller In this coupled together and primary coils 6 and 7, the inductive effect is balanced and'no oscillations are produce: in the antenna circuit.

lVitlrthe key 14 up, the current from the generator 8 will divide equally between the two halves 6 and 7 of the primary coil. This is because these two halves are closely is independent of whether the coupling between the primary Because of this equal division of the current, the primary induces no electromotive force on the secondary 3 and thus no load due to the antenna is on the generator 8. All the load on said generator is due to the resistance 1-6. On the other hand, when the key down, no current from the generator 8 [Vs in the resistance 16, and the coil 7 induces 'a substantial energydn the coil 3. position of thekey, therefore, the antenna imposes a load on the generator, and the resistance 16 does not. By properly choosing the resistance 16 the load due to it in one position of the key and the load no to the antenna in the opposite position of the key may be made equal.

li hen the key is up the electromotive induced in the primary coil 6 and 7 by the secondary coil 3 acts upon a closed circuit 16, 12, i3, 10, l1 and lead to outer end of coil 7. loil 3, therefore, is in inductive relation with a coil in a closed circuit. The effect of coil 3 upon the frequency of the antenna circuit is, therefore, not that of its self induction but somewhat less than this because of the mutual induction between coil 3 and the primary. W en the key is down, the half 6 of the primary is without effect on the coil 3 because it is open circuited. The circuit of coil 7 is then closed through the lead 5, generator 8, lead 9, coils 10 and 11 in parallel, key and con-- nector shunting these coils, and the lead to outer end of coil 7. No inductance is introduced into this circuit by the-coils i0 anl 11 because they are connected in op position. The coil 7 is, thereforej'closcd through only the inductance of the genera tor 8. It is practically short 'circuited. T he effect of this short circuited coil upon the coil 3 and so upon the frequency of the antenna current is not, however, as great that of the coils 6 and 7 together because the number of turns in coil 7 is smaller than in coils 6 and 7 combined. With the key down, therefore, the frequency of the antenna current is materially greater than with the key up.

The frequency with the key up may be below any radio frequency and may be of the order of 1000 cycles, whereby. it is substantially impossible for theantenna to propagate radio-waves during the periods. It is not contemplated that there will be an appreciable currentinduced in the antenna c ing periods, since the two troller primary windings induce currents in opposite directions which will substantially cancel each other, but my system has the added advantage that the natural frequency of the antenna is changed simultaneously with. the change in the position of the key and the natural trcquen'cy in the up position of the key is below radio frequency.

Since the frequency of the antenna may be made to change in the ratio of say, 23 to l, by my system, and, since the radiation is lowered as the square of the frequency, any tendency for the antenna to radiate when the key is up is greatly reduced.

There is substantially no transient flow 'of current during the changes between the on and off positions of the key. When thekey is quickly moved from up position to down position, the current flowing in the upper coil 6 will continue to flow until the zero non-signaling rcuit during the non-sigi'iaL. halves of the conpoint of the cycle is reached. During the next succeeding half-wave, no current will flow in said coil, the inductive elfect being transferred to the corresponding lower coil 7, in much thexsame manner as in the well known rectifier connection wherein a directcurrent load is connected between a midtap of a transformer winding and a pair of asymmetric conductors orcommutators con nected to the respective ends of said trans former winding.

By means of my invention, therefore, there can be no sparking at the contacts 12 and 15 for a longer period than a half-cycle of the radio-frequency current.

I have shown the transformer 4- and the balancing inductance device 10, 11 as being provided with iron cores, respectively. This is highly desirable when the reduction in frequency of the antenna circuit is designed to be of the order of 25 to 1 since very high inductances are necessary under those conditions. However, certain features of my invention may be utilized without employing the iron cores and without employing a tight coupling between the antenna coupling coil 3 and the primary coupling coils 6 and 7. It is to be understood also that the showing of the key 14: is entirely conventional and that any well-known type of key, such as a quick-acting key or a key with over-lapping contacts, may be employed, as will be obvious to those skilled in the art.

While I have shown a preferred embodiment of my invention in the appended drawing, I do not wish to be restricted thereto but I desire that only such restrictions shall be placed upon my invent-ion as are set forth in the appended claims.

I claim as my invention:

1. A modulating system including a main inductance winding having an intermediate tap, an auxiliary inductance winding having an intermediate tap, a translating device connected between said intermediate taps and means for changing the relation of said translating device to said main inductance so that the inductive reactance thereof either is, or is not, effectively related to said translating device.

2. A radio system including a main circuit and modulating means coupled thereto, said modulating means including a main inductance winding having an intermediate tap, an auxiliary inductance winding having an intermediate tap, a radio-frequency translating device connected between said intermediate taps and means for changing the relation of said translating device to said main inductance so that the inductive reactance thereof either is, or is not, effectively related to said translating device.

3. A modulating system including a main inductance winding having an intermediate tap, an auxiliary inductance winding having an intermediate tap, a translating device connected between said intermediate taps, a conductor connecting one end of said main winding to one end of said auxiliary winding and means for connecting the other end of said auxiliary winding either to the other end of said main winding or to said conductor,

4. A modulating system including a main inductance winding having an intermediate tap, an auxiliary inductance winding having an intermediate tap, a translating device connected between said intermediate taps, a conductor connecting one of said main winding to one end of said auxiliary winding, a second translating device connected to the other end of said main winding and means for connecting the other end of said auxiliary winding either to said second translating device or to said conductor.

5. A radio system including a main circuit and modulating means coupled thereto, said modulating means including a main inductance winding having an intermediate tap, an auxiliary inductance winding having an intermediate tap, a radio-frequency translating device connected between said intermediate taps, a conductor connecting one end of said main winding to one end of said auxiliary winding and means for connecting the other end of said auxiliary winding either to the other end of said main winding or to said conductor.

6. A radio system including a main circuit and modulating means coupled thereto, said modulating means including a main in ductance winding having an intermediate tap, an auxiliary inductance winding having an intermediate tap, a radio-frequency translating device connected between said intermediate taps, a conductor connecting one end of said main winding to one end of said auxiliary winding, a second translating device connected to the other end of said main winding and means for connect ing the other end of said auxiliary winding either to said second translating device or to said conductor.

7. A modulating system including a main inductance winding having an intermediate tap, an auxiliary inductance winding having an intermediate tap, a conductor connecting said mid-taps, a second conductor con necting one end of said main winding to one end of said auxiliary winding and means for connecting the other end of said auxiliary winding either to the other end of said main winding or to said second couductor.

8. A radio system including a main circuit and modulating means coupled thereto, said modulating means including a main inductance winding having an intermediate tap, an auxiliary inductance winding having an intermediate tap, a conductor connecting said mid-taps, a second conductorconnecting one end of said main winding to one end of said auxiliary winding and means for connecting the other end of said auxiliary winding either to the other end of said main winding or to'said second conductor.

9. The combination with a tuned circuit, of means for altering the inductance insaid circuit, and means for inductively utilizing the inductively stored energy in such man ner that the frequency of the tuned circuit is altered Within a period not exceeding one half of a cycle.

10. A system for controlling antenna current comprising a tuned antenna circuit, an inductance coil therein, a controller primary inductance device inductively coupled to the antenna inductance coil, a balancing inductance device, a source of high-frequency current coupled to the middle points of the controller primary and balancing inductance devices and means,-including said primary and balancing inductance devices, for changing the natural frequency of the antenna within a maximum time of one-half cycle of alternation.

11. The method of controlling theradiation of an antenna'circuit whichconsists in,

causing said circuit to have either a radiofrequency or a frequency at which radiation is substantially impossible. v

12. A system for controlling antenna current comprising a tuned antenna circuit, an inductance coil therein, a controller primary winding inductively coupled to said antenna. inductance coil, a source of higlrfrequency current and means for so controlling the flow of high-frequency current through said controller primary winding that the; inductive effects will cancel one another.

13. A system for controlling antenna current comprising a tuned antenna circuit,- an inductance coil therein, a controller primary winding inductively coupled to said antenna inductance coil, a balancing inductance device, a source of high-frequency current connected to middle points of said controller primary winding and said balancing inductance device and means for so controlling the flow of the current through the controller primary winding and the balancing inductance device that the high-frequency source may be inductively or non-inductively associated with said antenna circuit.

14 A system for controlling antenna current comprising a tuned antenna circuit, an inductance coil therein, a controller primary inductance device inductively coupled to the antenna inductance coil, a balancinginductance device, a source of high-frequency current connected to the middle points of the controller primary and balancing inductance devices and means for changing the natural frequency of the antenna and simultaneously controlling the flow of current through the controller primary and balancing inductance devices to alter the coupling between the high-frequency source and the antenna circuit.

15. A system for controlling antenna current comprising a tuned antenna circuit, an inductance coil therein, a controller primary inductance device inductively coupled to the antenna inductance coil, a balancing inductance device, a source ofhigh-frequency current connected to the middle points of the controller primary and balancing inductance devices, means for so directing the high-frequency current through the controller primary inductance device as to cancel the inductive effects and means for so controlling the circuit through the controller primary inductance device as to produce an inductive effect, the coupling being such that, when thefirst mentioned means is operative, the antenna may oscillate at the normal radiating frequency and, when the second-mentioned means is operative, the oscillating frequency is lowered.

16; A system for controlling antenna current comprising a tuned antenna circuit, an

inductance coil therein, a controller primary inductance device inductively coupled to the antenna inductance coil, a balancing inductance device, a source of high-frequency current coupled to the middle points of the controller primary andbalancing inductance devices, a key, contacts operated by the key to direct the high-frequency current through the controller primary inductance device to 3 cancel the inductive effects and contacts operated by the key for controlling the circuit through the controller primary inductance device to producean inductive effeet, the circuits being so arranged that the current from said source flows non-indue tively through said balancing inductance device,

17. A system for controlling an antenna current comprising a tuned antennacircuit, a source of high-frequency current and modulating means inductively coupling the high-frequency source and the antenna circuit, whereby the natural frequency of the antenna circuit is raised simultaneously. with delivery of power and lowered with cut-off of power. a I

18. The combination with asupply circuit, of a pair of shunt circuits including oppositely-wound transformer coils connected to said supply circuit, the magnetizing effects of said coils being normally substantially neutralized, means for varying the relative magnetizing effects of said coils,

and a secondary circuit in inductive relation to said coils. V

19. The combination with a high-frequency supply circuit, of a pairv of shunt circuits including oppositely-Wound transformer coils connected to said supply circuit, a tuned secondary circuit in inductive relation to said coils, and means for varying the energy supplied to said secondary circuit, said means including means for varying the relative magnetizing effects of said coils, and means for maintaining a substantially constant total load on said suppl circuit.

In testimony whereof, I have hereunto subscribed my name this 16th day of June,

CHARLES LE Gr. FORTESCUE. 

